I bought 2 of the 4' wings from a cultipacker last year. I think it was 125 per section or 225 for both. Got a couple extra wheels he had laying there also. They must have broken some in the past other wise why would there be spares ? I was thinking of making a double four foot or making an eight foot from all the parts.
At farm auctions they go ( 8' models ) fairly high, 3-8 hundred depending on style. I have never seen a double row up close.